package org.semanticweb.yars.nx.hash;
/*
 **************************************************************************
 *                                                                        *
 *          General Purpose Hash Function Algorithms Library              *
 *                                                                        *
 * Author: Arash Partow - 2002  										  *
 * Modified: Aidan Hogan - 2010                                           *
 * URL: http://www.partow.net                                             *
 * URL: http://www.partow.net/programming/hashfunctions/index.html        *
 *                                                                        *
 * Copyright notice:                                                      *
 * Free use of the General Purpose Hash Function Algorithms Library is    *
 * permitted under the guidelines and in accordance with the most current *
 * version of the Common Public License.                                  *
 * http://www.opensource.org/licenses/cpl1.0.php                          *
 *                                                                        *
 **************************************************************************
 */


public class HashLibrary {

	public static long RSHash(String str)
	{
		int b     = 378551;
		int a     = 63689;
		long hash = 0;

		for(int i = 0; i < str.length(); i++)
		{
			hash = hash * a + str.charAt(i);
			a    = a * b;
		}

		return hash;
	}
	/* End Of RS Hash Function */


	public static long JSHash(String str)
	{
		long hash = 1315423911;

		for(int i = 0; i < str.length(); i++)
		{
			hash ^= ((hash << 5) + str.charAt(i) + (hash >> 2));
		}

		return hash;
	}
	/* End Of JS Hash Function */


	public static long PJWHash(String str)
	{
		long BitsInUnsignedInt = (long)(4 * 8);
		long ThreeQuarters     = (long)((BitsInUnsignedInt  * 3) / 4);
		long OneEighth         = (long)(BitsInUnsignedInt / 8);
		long HighBits          = (long)(0xFFFFFFFF) << (BitsInUnsignedInt - OneEighth);
		long hash              = 0;
		long test              = 0;

		for(int i = 0; i < str.length(); i++)
		{
			hash = (hash << OneEighth) + str.charAt(i);

			if((test = hash & HighBits)  != 0)
			{
				hash = (( hash ^ (test >> ThreeQuarters)) & (~HighBits));
			}
		}

		return hash;
	}
	/* End Of  P. J. Weinberger Hash Function */


	public static long ELFHash(String str)
	{
		long hash = 0;
		long x    = 0;

		for(int i = 0; i < str.length(); i++)
		{
			hash = (hash << 4) + str.charAt(i);

			if((x = hash & 0xF0000000L) != 0)
			{
				hash ^= (x >> 24);
			}
			hash &= ~x;
		}

		return hash;
	}
	/* End Of ELF Hash Function */


	public static long BKDRHash(String str)
	{
		long seed = 131; // 31 131 1313 13131 131313 etc..
		long hash = 0;

		for(int i = 0; i < str.length(); i++)
		{
			hash = (hash * seed) + str.charAt(i);
		}

		return hash;
	}
	/* End Of BKDR Hash Function */


	public static long SDBMHash(String str)
	{
		long hash = 0;

		for(int i = 0; i < str.length(); i++)
		{
			hash = str.charAt(i) + (hash << 6) + (hash << 16) - hash;
		}

		return hash;
	}
	/* End Of SDBM Hash Function */


	public static long DJBHash(String str)
	{
		long hash = 5381;

		for(int i = 0; i < str.length(); i++)
		{
			hash = ((hash << 5) + hash) + str.charAt(i);
		}

		return hash;
	}
	/* End Of DJB Hash Function */

	public static long JavaHash(String str)
	{
		long seed = 31;
		long hash = 0;

		for(int i = 0; i < str.length(); i++)
		{
			hash = (hash * seed) + str.charAt(i);
		}

		return hash;
	}
	/* End Of Java Hash Function */

	public static long DEKHash(String str)
	{
		long hash = str.length();

		for(int i = 0; i < str.length(); i++)
		{
			hash = ((hash << 5) ^ (hash >> 27)) ^ str.charAt(i);
		}

		return hash;
	}
	/* End Of DEK Hash Function */


	public static long BPHash(String str)
	{
		long hash = 0;

		for(int i = 0; i < str.length(); i++)
		{
			hash = hash << 7 ^ str.charAt(i);
		}

		return hash;
	}
	/* End Of BP Hash Function */


	public static long FNVHash(String str)
	{
		long fnv_prime = 0x811C9DC5;
		long hash = 0;

		for(int i = 0; i < str.length(); i++)
		{
			hash *= fnv_prime;
			hash ^= str.charAt(i);
		}

		return hash;
	}
	/* End Of FNV Hash Function */


	public static long APHash(String str)
	{
		long hash = 0xAAAAAAAA;

		for(int i = 0; i < str.length(); i++)
		{
			if ((i & 1) == 0)
			{
				hash ^= ((hash << 7) ^ str.charAt(i) * (hash >> 3));
			}
			else
			{
				hash ^= (~((hash << 11) + str.charAt(i) ^ (hash >> 5)));
			}
		}

		return hash;
	}
	/* End Of AP Hash Function */


	public static long hashCode(String str){
		return JavaHash(str);
	}

}
